Ingot mold lining



Patented Dec. 23, 1941 INGOT MOLD LINING Gerhard Behrendt,Duisburg-Ruhrort, Germany, assigner to August Thyssen HtteAktiengesellschaft, Duisburg-Hamborn, Germany, a body corporate:Application April 21, 1939, Serial No. 269,245

6 Claims.

In the ordinary unlined molds made of thick walled cast iron, deadwelding with subsequent casting pores 4are easily caused by the suddencooling effect of the cold mold walls, for example when casting killedsteel, because the liquid 'surface of the ingot solidies at the edgessubjected to the strong cooling effect of the mold wall, remainsadhering thereto and is washed over. Moreover, the transcrystallizationcaused by the strong conducting off of heat by the mold walls preventsthe separation 'and rising of the non-metallic substances, especially ofthe products of deoxidation, in that these particles after being formed,have not suilicient time to rise in the interior of the liquid ingotbefore their path is blocked by the crystallites growing in from thesides, consequently they become imprisoned in the ingot. The cause forthe formation of secondary pipes during the casting of Iingots which arelong in proportion to their thickness in ordinary chill molds is alsoonly due to a too rapid beginning of a solidication of the ingot. as theingot then easily solidies sooner in the middle portion than at the headand base. with the result that the passage downwards into thecontraction and shrinkage cavities is barred to the liquid materialcollected in the head ofl the ingot.

Another example of the detrimental eiiect of a too rapid conducting offof heat through the ordinary casting molds is the ring of bubblesoccurring in the unkilled steels, whose formation is explained by thefact that the gas bubbles formed cannot escape upwards owing to thestrong transcrystallization but hang on the pointed crystallites.

The chilling effect of the cold mold also has the disadvantage that,when casting large ingots, cracks frequently form especially in thelongitudinal direction of the ingot. These cracks form the more easilythe more sensitive the material of the ingot is to tensile stressingunder heat.

lConsequently, experience has shown that great diiilculties areencountered in casting or in centrifuging Thomas steel in molds of largediameter.

It has therefore been proposed, to cast large round ingots, for examplefor gun barrels and ships shafts in cast iron molds, which ought to havea thick lining of some refractory material, such as silica material. Thethick refractory lining is intended to very considerably slow thecoolingI and to avoid the above mentioned defects. The cost of producinga thick Germany July 9, 1937 The object of the inventionp'is to renderit possible to produce large cast ingots which must be free from surfacedefects.

, It has been found, that it is possible to produce such lined molds bycasting the mold with a very thin lire-proof lining having great densityand high mechanical strength, such as can be obtained by a specialmixture of different sizes of grain.

If those particles of asubstance whichpass through a sieve with meshwidth of 4 mms. and remain lying on a sieve with a 2 mm. mesh width aredescribed as coarse, those particles which pass through a sieve with 2mm. mesh width and remain on a sieve with 0.85 mm. mesh width aredescribed as medium sized and those particles which pass through a sievewith 0.85 mm. mesh width are described as fine, the composition can bemixed for example of coarse and 60% fine grains, or of 40% coarsegrains, 40% medium.

grains and 20% fine grains. With such mixtures a dense lining havinghigh physical strength to resist the mechanical action of liquid castingmaterial is obtained after the sintering of the refractory liningintroduced into the mold.

The thin refractory lining according to the invention can be produced bylining the mold with thin stones or preferably by ramxning orcentrifuging the refractory material into the mold.

Moreover, it; is advisable according to the invention to produce therefractory lining from a mixture of different materials whoseexpansionsunder heat are contrary to one another, so that neither during thedrying operation nor during the casting operation an expansion orcontraction of the refractorymaterial take place.

Thus, a working in or possibly a detaching of the lining from the moldis prevented. Such a lining may, for example, have the following lsuliite liquor. v

mental expansion of the iron can then be ac- ,v

It may be advisable,v to assist the adhesion of the thin layer of thelining by embedding iron wires or rods in the mass. IThe knowndetricounted' for by the composition of the lining mass. Metalinsertions, such as iron rings, are

fire-proof lining for molds is, however, so 'high 55 also preferablyembedded at different planes in the refractory lining for obtainingrapid cooling.

As the mold has a cooling effect. the lining, if it is made according tothe invention, is not burnt through quite so strongly as is otherwiseusual for refractory masses. On the other hand, the lining is subjectedto higher wear chieily at its lower and upper ends by the stripping ofthe ingot.

It is therefore advisable to secure the edges of the lining at the topand at the bottom by rings oi' more solid material.

Several embodiments of the invention are illustrated by way of examplein longitudinal section one in each of the figures of the accompanyingdrawing, in which I designates the mold,` 2 the ingot and 3 the lining.l

According to Fig. 1 the lining is protected at the top and bottom byrings l of previously strongly burnt and consequently wear-proofrefractory plates. According to Fig. 2 for example the lining is securedat the top by an iron ring 5 which may be loosely inserted or screwedinto the mold, whereas at the bottom the mold has an annular shoulder 6of the thickness of the lining. v

On the other hand itis possible to arrange such rings for securing thelining in other planes than only at the top and bottom. Figs. 3 and 4,for example, show longitudinal sections of molds with such types ofconstruction. These rings 1 may be loosely screwed in (Fig. 3) or form apart 8 of the mold wall (Fig. 4). These rings evidently exert a coolingeffect and reduce the checking effect to the heat flow produced by thefractory lining according to the invention against the action of thecasting material and of the slags, may also be used to advantage withoutdeparting from the scope of the invention.

lining. This cooling is intensified the more the thickness of the liningis reduced. In Figs. 5 and 6, for example, loose rings 9v and rings I0forming part of the mold wall are shown, which rings extend rightthrough the lining and consequently have 'a strong cooling effect. By/varying the number and thickness of these rings it is possible toregulate the cooling speed to suit the desired purpose.

To ensure ingots which are as smooth as possible, it is advisable afterthe refractory lining has been fitted in the mold, to smooth its surfacewith the aid of a template or to grind it smooth with the aid of agrinding machine.

Other known measures, which increase the chemical and mechanicalresistance of the re- I claim:

1. An ingot mold lining for casting heavy steel ingots suitable forrepeated use, including a thin lining body of refractory material, saidmaterial being composed of a mixture of grains of burnt chamotte. freshclay and quartz with different sizes sintered to a high strength toresist the mechanical action of the casting material, the expansioncoefficient of the different composite parts of the refractory materialbehaving oppo- -sitely' under heat so that expansion and contraction donot occur during drying and casting.

2. A lining as specified in claim 1, in which the mixture is composed of40% coarse and 80%"y fine grain material.

3. A lining as specified in claim 1, in which the mixture is composed of40% coarse, 40% mex dium and 20% ne grain material.

4. A lining as specified in claim 1, in which the mixture is composed ofburnt chamotte '75%, fresh clay 13% and quartz 12%.

5. An ingot mold lining for casting heavy steel ingots adapted to beused repeatedly, which comprises a metal mold lined with a thin coatingof refractory material composed of particles of different size adaptedto increase the density and strength of said refractory and consistingof a major portion of burnt fire clay with minor proportions o freshclay and silica in amount suflicient to vreduce the expansion coeflcientof said material to the point at which substantially no expansion andcontraction takes place during drying and casting.

6. An ingot mold lining for casting heavy steel ingots adapted to beused repeatedly, which comprises a metal mold lined with a thin coatingof refractory material composed of a major proportion of relativelycoarse particles of burnt fire clay and minor proportions of fine freshclay and fine silica in amount suiiicient to reduce the expansioncoefficient of the material to the point at which substantially noexpansion and contraction takes place during drying and casting.

GERHARD BEHRENDT.

